The work reported in this book is dedicated to the theoretical study of the certain properties of several types of resonant and nonresonant photonic nanostructures. Negative refraction at the side edge of a Bragg reflector is studied. It is shown that a new effect, spatial oscillation of the Poynting vector of the transmitted radiation, can be observed under certain circumstances. Analytical theory is developed explaining the measured reflectivity spectra of a one-dimensional photonic crystal with quantum wells embedded in its layers. Theoretical modelling of the parametric amplification in the structure is performed, yielding results which show good agreement with the experimental measurements. Theoretical formalism and corresponding software code have been developed to model the kinetics of polariton laser. The model is based on a Boltzmann equation approach and accounts for electrical or optical pumping, polariton decay, and polariton-acoustic phonon, polariton-free electron and polariton-polariton scattering. Software code has been used to model the main characteristics of specific GaN-based polariton lasers using parameters provided by experimental collaborators